1. Field of the Invention
The present invention relates to a valve for controlling fluid flow, and particularly to a valve which is readily converted to function as a by-pass valve or a backwash valve.
2. Description of the Prior Art
The present invention has particular application to the control of a water softener having a tank containing material through which hard water is passed for softening. It is often desirable to by-pass or redirect the water flow so that it does not pass through the tank, such as when the water softener equipment is to be repaired or when the user plans to be away for an extended period of time and wishes to shut down the softener. A so-called by-pass valve is used to do this. Such a valve is also commonly used in non-automatic types of water softeners, in which the tank is periodically replaced with one having a fresh charge of softener material.
My U.S. Pat. No. 3,643,692, entitled "Valve," and issued Feb. 22, 1972, discloses a typical by-pass valve operative to perform the functions just described. Although the valve generally operates satisfactorily, there are a number of areas in which improvements are desirable. For example, it has been found that the use of O-rings for sealing purposes is not completely satisfactory in that the O-rings tend to abrade during travel across valve ports. Also, in some instances unusually high pressures have rolled or pinched the O-rings such that undesirable leakage occurs. Further, the passage within which the O-rings travel sometimes becomes scaled or corroded over a period of time, and it is difficult to slide the O-rings over this material. Also, the material of the O-rings tends to bond or migrate into the pores of the brass material of which such a valve is usually made, which tends to prevent slidable movement of the O-rings.
Another problem with the O-ring type of valve disclosed in the patent is that the water flow is usually full on or full off because the valve stem is a push-pull type. It is often desirable to provide a slower flow of water on initial filling of a softener tank.
The by-pass valves of the aforementioned patent, as well as most by-pass valves of the prior art, are able to perform only a by-pass function and there are situations where this is unduly limiting. For example, where a by-pass valve is to be used in conjunction with water treatment equipment in the form of a sand filter or the like for filtering impurities out of the water, it is desirable not only to be able to bypass the equipment during its repair or replacement, but also periodically to reverse the flow of water to backwash the filter. At present the usual by-pass valve is supplemented with a second valve to perform the backwashing operation. It is preferable to have a single valve adapted for easy conversion from a by-pass operation to a backwash operation.